Telephone-exchange system



L. A. MORTIMER.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED AUG.24. 191a.

Pa'tentedi July 5 1921 //7 van/0 L 0 11/25 A Morfimer.

UNITED STATES PATENT-OFFICE? Louis A. MORTIMER, on NEW YQRK,'1\T. YQ, Assi'snoit 17o wnsrnltn nnncrmc COMPANY, INCORPORATED, onnnw YOBK, N. Y., A CQRPORATIJVIONIOF NEW YORK.

' Insuch system,'especi'ally those in which long distance or'toll lines are employed, 1t is often desirable that switching centers or switchboards' usually designated as through switchboards, forinterconnecting such lon distance lines, be located at stations, or' switchboards separate fro'm'tnose at which connections are madewith the local lines, commonly called terminating switchboards, or those at which calls the line, commonly called outward switchboards. It is essential incases of this nature that suitable signaling means be provided wherebytheoperatoratone such switchboard may notify the operator at another switchboard when a call is to be-handled by the operator at the latter switchboard. However, due to the fact that the through switchboard is often'located at a considerable distance fromthe terminating switchboard, it is also desirable to eliminate all unnecessary conductors interconnecting such switchboards.

' usual talking conductors of the line circuit,-

It is theobject of this invention to provide'a simple and inexpensive system of, this nature in which the signaling between certain switchboards, at which terminals of the line are located, is performed over the thus eliminatingseparate signaling conductors therebetween. 1

To attain thisobject, in accordance with a feature of the invention, means associated with the talking conductors of the line circuit is provided at each switchboard which cooperate upon the receipt of an incoming call to impress current of one polarity on the individual talking conductors andthereby cause the operation of-the calling signal device at one switchboard and to simultane ously operate a busy signal at the other switchboard.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Pat'ent. Application fiiea'n'ugust 2 4, 1918.

' polarityr are originated over Serial No. 251,266. v l

- In accordance with a second feature of the invention, .operator controlled means as sociated with the talking. conductors of the line circuit is also provided at one switchboard to impress current of a different on the individual talking conductors of the line circuit and thereby cause the display of the calling signal at the other ofi ice in case the operator at the first switchboard wishes to tran'sferI the call to such switchboard. i

' In accordance with a third feature of the .1nvention,-means are provided whereby the subsequent recalling of the calling station upon the completion of the connection by the "operator at one switchboard may be ac complished over. the talking conductors of the line without interfering with the signaling apparatus at the other switchboards.

These and other features not specifically mentioned above will more fully. appear from the following specification and the an neXed drawing, in which the figure shows diagrammatically the terminus of a telephone line circuitassociated with the' various classesjof switchboards and embodying the invention, together with-s ufli cient portions of a suitable associated connecting circuit to properly. illustrate the invention In the accompanying drawing the I transmission line,comprising conductors l and 2,

P tented July 5, 1921.

is provided with jacks 46, 2 5andj32 at the outward terminating and through "switchboards X, Y a'nd'Z, respectively. At each of the switchboards a plurality of suitable 'link circuits A is provided for connection with the jacks. Switchboard X is adapted for handling, originating or' outwa'rdcalls and a calling signal lamp 4A is associated with jack 46 thereat by meansof which calls may be transferred thereto by the operator at switchboard Y. Switchboard Y is'adapt ed for receiving incoming. calls, which'are indicatedthereat by acalling signal lamp 22 associated with the jack 25. Switchboard Z is adapted'for handling through calls which may be transferred thereto by the operator at switchboard Y responsive to the actuation ofthe'key 27 and indicated atswitchboard Z by calling signal; lamp 4L8. Signaling.

switchboards X, Y and Z respectively, to in dicate the busy condition of the transmis sion line when engaged in'connectionwith any call.

,lamps 10, and 18 are provided at the;

' boards .1 and. Z,

It is thought that the invention may be more fully understood from the following description of the operation of the system shown on the drawing. Upon the receipt of an incoming call, originated by the applicaalternating current to the conductors 1 and 2. at a distant station, not shown, relay 3 operates, causing the operation of relay 6, over a circuit extending from battery, through the winding of relay 6 and the'contact of relay. 3 to. ground; Relay 7 is-operated over a circuit established from battery through the winding ofrelay 7 and the alternate. contact of relay 6 to ground. Relay? isthereupon locked in an operated position. over'a. circuit extending from battery,. through the. winding and the righthand inner alternate contact ofrelay 7 and thefnormal. contact of relay 8 toground. Calling signal lamp. 22is lighted over circuit extending from battery, through the left-handouter alternate contact oi relay 7, the left-hand normal contact of relay 23 and the lamp-221150 ground. Busy signal lamps 9 and 10 at switchboards Y and X respectively, are also lighted over a circuit established from'battery, through the left-hand inner. alternate contact of relay 7 the righthand normal contact of relay 11 and the lamps 9. andlO in-multiple to ground. 'By the; closure of the right-hand outer alternate contact of relay 7, a circuit is completed frombattery, through the right-hand outer alternate contact; of relay 7, the upper windtion of grounded ingzof retardation coil12, the tip conductorof the section ofthe line connecting switchthe right-hand: winding oi? retardation coil 13, the winding of polarized relay 1 1, the right-hand normal contact of relay 15and' the winding of. relay 16 to ground. Since relay 14: is unresponsive to the direction of flow of the current in this circuitsuch relay does not operate, althoughrelay 16 operates, causingthe operation of relay 17-, over a circuit established from bat: tery, through the winding ofrelay 17 and the contact of relay 16 to ground. The 010- sure of the right-hand contact of relay 17 causes the lighting; of busy signal lamp 18 overa circuit extending from battery through the right-hand contact of relay 17 and the-lamp 18 to ground. The closure of the left-hand contact of relay contact of relay 1.7, the normal. contact of coil 13, the ring conductor ofthe section of transmission line joining switchboards Y and Z, the lower winding of retardation coil 12, the winding of retardation coil 19, the winding of relay 20 and the winding of relay, 21 to ground. As in the case of the circuit traced for relay-145, thedirection of current flow is such that relay 20 does not oper ate. However, relay 21 operates, causing 17, completes acircuit' from battery, through the left-hand the operation of relay 11 over a circuit extending from battery, through the winding of relay 11 and the contact of relay 21 to ground. By the opening-of its left-hand' normal contact relay 11 opens the bridge including relay 3, byclosing its left hand alternate contact completes the bridge including relay a and condenser 37, and by closing its right-hand. alternate contact completes a circuit for busy signal lamps 9 and 10 from battery, through the right-hand alternate contact of relay 11 and the lamps 9 and 10, inmultiple, to ground, thereby replacing the former circuit for lamps 9 and 10, which was openedbythe opening of the right-hand normal contact of relay 11. 7

Although relay 5 is also normally bridged across the line in. serieswith condenser 36, such relay is notresponsive to the incoming rlngi'n g current operating relay 3,v due to the shunting effect of the grounded bridges,.one of which includes the lower Winding of coil 12 and its associated condenser and the other. of which includes the condenser associated with the lett-handwinding of coil. 13, whereby relay-5 receives aninsutficient amount of current to cause its operation. 'Although relay 4': may respond to such ringing currentin case the application thereof is. continued after the operation of relay 11, the polarity of current thereby impressed upon the tip conductor leading to the switchboard Y agrees with that supplied to such. conductor through the right-hand. outer alternate contact of relay 7 sothat theapparatus associated with such. tip conductor is unaffected by the operation of such relay. I The operator atswitchboard Y,-observ ing the lighted condition of lamp 22, inserts plug 24, of cord circuit A thereat, in jack 25,.thereby' operating relay 8 over acircuit extending from battery, through resistance 45, the sleeve contacts of .plug 2t and jack 25, the right-hand normal contact of relay 23 and the winding of relay 8 to ground. The opening of the normal contact: of. relay 8, opens the locking circuit of, and causes the release of relay, 7 Although the open-v mg of the right-hand outer alternate contact of relay 7' removes battery from the circuit previously traced tor relays 14 and 16, relay 16 is not released since battery of the same polarity is connected, thereto through the normal contact of relayf26, the middlealternate contact of relay- 8. andthe right-hand normal contact of relay 7. The. busy signal lamp 18 is therefore maintained 111 a lighted condition. A locking circuit is also established for relay 11 from battery,

through the windingof relay 11 and the leftand 11. Lamp 22 is extinguishedby the 1 tact of relay 28, the left-hand tact of rel'a-y28 and the mal contact 1t" releases reestablishing the bridge including conopening "of. the left-hand outer alternate contact of relay 7. Relay 29 "is operated over a circuit established from battery, through the winding of relay 29 and the contact 30of relay '8 to ground, thereby disconnecting the tip and ring conductors ofthe section of thetransmission line joining switchboards Y and'Z'from the jack 25 and the conductors 1 and 2"of thetrans mission line. Relay 34 is also Operated, due to the operation-of relay' 8, over acircuit established from battery, through the Windingof relay 34'and the contact 31 of relay 8 to round' I r I i Althoug not shown on the drawing, since it is not essential to the proper understanding of the invention,the cord circult A may be provided with any Suitable 'form of switching arrangement whereby the operators' telephone set, also not shown, may be connected withsuch cord circuit; V

Upon ascertaining that the connection desired, is such that the call should be handled by the operator at the through switchboard Z, the operator at switchboard Yv actuates the non-locking key 27 thereby operating relay 26 over a circuit established from battery, through the winding of relay 26 and the contact ofkey 27 to ground. The opening of the normal contact of relay 26 removes the battery supply from the circuit including relays 14 and 16 and the closure of the left-hand alternate contact substitutes therefor a battery adapted to supply current of the opposite polarity. Such current operates relay 14, while 16 is maintained operated. 'Relay28 is operated over a circuit extending from battery, through the winding of relay 28, and the contact of'relay 14 to ground. The closure of the left-hand alternate contact of relay 28, completes a locking circuit for such relay extending from battery, through the wmding and the left-hand alternate conmiddle normal contact of relay 15 to ground. lighted over a circuit extending from battery, through the right-hand alternate connormal contact of relay 15 and the lamp 48 to ground. The

' opening of the middle normal contact of relay 28 opens the bridge including the condenser 36 and the relay 5. 7

When the operator at switchboard Z answers the transferred call by the insertion of plug 24 of a'cord circuit A thereat into the jack 32, the relay 15 operates over a circuit from battery, through the resistance '45, the sleeve contacts of plug 24 and jack 32 and the winding of relay 15 to ground. By'the opening of its {left-hand normal contact, relay 15 extinguishesthe lamp 48; by the-opening of'its middle norrelay 28, thereby key 35, in cord circuit A Lamp 48 is e and by the closure of its left-hand alternate contact it completes a holding circuit for relay 17, from battery, through the winding of relay denser 36 and the relay5;

.l7'and the left hand alternate"contact of relay '15 to ground] The opening of the The operator at switchboard Y'removes the plug 24, of the cord circuit A, thereat,

. from jack 25, thereby reestablishing the continuity of the lineconductors from the distant station to the switchboard Z,"through the-release 'of'relays 8 and' 29, asw'ell as causing the release of relays"26,"-14,'and'34,

but maintaining busy lamps 9; and 10 in a V lighted condition due to the continued operation of relay'sli, 21- and 11'. 7 j

After the operator at switchboard Z has prepared the connection "desired, it is the usual: practice-to signal the distantstation on the transmission line, indicating that the connection may be completed thereat, andthe conversation may proceed. This is accomplished by the actuation; of ringing at switchboard Z, whereby :relay 5 is operated over a circuit established from the source of ringing current through the'lower alternatecontact of ringing-key 35, the ringcontacts of plug 24 and jack 32,-the lower normal contact of relay38, the right-hand'nor'mal contact of relay 28,-the'condenser-36, the winding of relay 5, the upper normal contact of relay-38, the-tip: contacts of jack 22 and plug 24 and the upper alternate contact of-key 35 to ground; The operation of relay 5 changes the" polarity of thecurrent. flowing through relays 20and 21, thereby causing the "operation of relay 20 -while maintaining relay 21in an operated 'Icondition. The operation. of relay 20 causes the operation of relay 29' over a circuit established from battery through the winding of relay 29' and the contact of relay 20 to ground. Re lay 29, in operating, disconnects the tip and ring conductors of thesection of the transmission line'connecting switchboards' Y'and Z, from the line'conductors 1 and 2 leading to the distant station,andconnect's a source of ringing current thereto, through the' normal contacts 'ofrelay 34-and the alternate contacts of relay 29 tocause the operation of a suitable signaling device atthe distant station,- not shown." Upon."the release of ringing key 35,-theresponsive apparatus re-Q conductors l and hand alternate contact of relay 7 11,, the middle normalcontact of relay 29, the con: denser 37 the winding of relay 4, and the upper normal contact of relay 29 causesthe opeliationof relay t, thereby completing a circuit extending from battery, through vthe contact of relay 4t and the upper winding of retardatron coil 12, the tip conductor of the section of the line. connecting switchboards Y and Z, the right-hand winding of retardation. coil 13, the winding of relay 14:, the right,- handalternate contact of relay 15 and'the windingof relay 33 toground. Due to the direction of flow of current within such circuit, relay let does not, operate, but relay 33 operates and causes the operation of relay 38, over a circuit completed from battery through the winding of relay 38, the .lefthand normal contact of relay 28 and the contact of relay 33 to ground; Supervisory relay 39 in cord circuit A, is-thereupon op; erated over a circuit established from the source of ringing current,through the lower alternate contact of relay 38, the ring contacts of jack32 andjplug 24:, the lower normal contact of ringing key-35, the winding of relay 39, the uppernormal, contact of ringing key 35?, the-tip contacts of plug21 andjack32 andthe upper alternate contact of relay. 38 .tog ound. Supervisory lamp 4:0 is-lighted over a circuit established'from battery, through the lamp 4L0 andlthe con:

tact of relay 39 to ground, thereby signaling the operator-at switchboard Z,

In case the operator at switchboard Y in answering the incoming call finds that the nature of the desiredconnection is such-that it should be handled through the outward switchboard X, which is usually located closely adjacent to;v the switchboard Y, the. call may be transferred thereto by the actuation of key lhthereby operating relay 23,

over circuit established from battery, through the windingof relay 23 and, the, contact of key 41 to ground; Relay 7 operates over a circuit established from battery, through the winding'of relay'7, the normal contact of relay, 6,,contacts 4:2 and 4 3 of relay 23 and the contact of key 4:1'to ground. Lamp 14:, at switchboard X islighted: over a circuit established from battery, through the left-handouteralternate contact of relay 7, theplett-hand alternate contact of relay 23 and; the lamp 44: to, ground. Relay, 8 is released, due to the opening of the right,- handnormal; contact of relay 23, thereby locking relay 7, over a circuit extending from battery,through the-winding andlthe right-hand inner alternate contact of, relay 7 and the normal ground. V

The busy si al'lamp Bis-maintained in a lighted condition and, relays:16,,17,,21 and contact of relay 8; to

arernaintained in an operated condition as previously described in'connection with theoriginal operation ofrelay7.

The operator at switchboard the plug 24:, of cord circuit A,'thereat, from the jack 25, and the operator at switchboard X answers the transferred; call-by theinsertion of theplug 24;, of a cord circuit A, at such switchboard into jack 46, whereupon relay 8 operates over a circuit extending from battery, through resistance 45, the sleeve contacts of plug-24, and jack 46 and the winding ofrelay 8 to ground. Lamp 4: 1 is extinguished, due to .the release of relay 7 caused by the opening ofthe normal contact. ofrelay 8, and the-other subsequent operations depending upon theoperation of relay, 8, result as previously described in connection with the answeringofthe in; coming call at switchboard Y a Y remqv s.

. It will thus be seen that by meansotthis and that effective means is also provided for V relaying the signaling I current past the retardation coils present in such section of the transmissionline.

What is claimed is: a

1. A telephone exchange system comp rise ing a transmission line circuit, aplurality of switchboards connected thereto, -a calling signal at one of the swltchboards, signal control means thereat responsive to signaling current on the line, a busy signal at anotherof vthe switchboards, means controlled by. the signal control meansfor impressing a current on one of the talking'condu'ctors of the line interconnecting the switchboards, and means at the second men tioned switchboard responsive thereto for operating the busy signal device. p

2. A telephone exchange system comprising a telephone line, a plurality of switchboards connected thereto, signal control means at one of the switchboardsresponsive to signaling current on, the telephone line, a calling signal device controlled thereby, a plurality of soureeslof current of different polarities, means controlled by the signal control means for connecting. one source of current at said one of the switchboards'to one line conductor interconnecting such switchboard and another switchboard, signal control means at the second mentioned switchboard responsive thereto, a busy signaling device at the second mentioned 7 switchboard controlled by the signalcontrol other source of current for the first mentioned source to impress current of adiflerent v I polarity upon the line conductor, means at the section of line circuitextending therefrom to the second mentioned switchboard, switching means responsive to the operation of the signal control means to connect one of 7 said sources to one conductor of the isolated section, signal controlmeans at the second mentioned switchboard responsive to current from any of said sources connected to such conductor to operate the busy signaling device, additional operator-controlled switch ing means at the first mentioned switchboard to selectively connect another of said sources to the conductor, and signal control means at the second mentioned switchboard responsive thereto to operate the second mentioned signaling device thereat. r

4. A telephone exchange system comprising a telephone line, a plurality of switchboards connected thereto, a callingsignaling device at one of the switchboards, a busy signaling device at another of the switchboards, a plurality of sources of current of different polarities at the 'first mentioned switchboard, means responsive to signaling current on the line to operate both signaling devices, said means including one of the sources of current, operator-controlled means at the-first mentioned switchboard to substitute for such source another source of current having a difi'erent polarity, and an other signaling device at the second switch? board responsive thereto. I

5. A telephone exchange system compris-y I ing a telephone line, a plurality of switchboards connected thereto, signal control means at one of the switchboards responsive to periodically varying current flowingthrough the line conductors in sem'atz'm, switching means responsive thereto to connect a source of current to an isolated conductor of the line circuit extending to another of the switchboards,"a signaling device at the second mentioned switchboard respon sive thereto, a link" circuit at 'the' secondmentioned switchboard for connection withthe line andmeans responsive to ithe con nection of the link circuit with the line for" maintaining the signaling device in operated condition independent of the signal-control" 6. A telephone exchange system comprising a telephone line, a plurality of switch.-

boards connected thereto at one end thereof,

operator-controlled means at one of the switchboards' for lsolating the portion of the line extending to another of the switchboards, a source of currentv at the first mentrolled means thereat "for connecting the tioned switchboard, additional operator-con source of current to one conductor of the isolated portion of theline, and'a signaling;

device at the second mentioned switchboard responsive thereto. 1 v I In witness whereof, Ihereunto subscrlbe my name this 19th day of August, A'. D.'19 18.' i i LOUIS A. MORTIMER. V 

